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Icelandic agriculture is characterized by the use of extensive rangelands for grazing and the making of
The underlying basis for Johannesson´s and
Nygard´s work was the US soil classification system (Baldwin et al.
, 1938). hay for winter feeding. Cultivated land is of limited extent. Iceland has therefore traditionally put more
Johannesson established a classification system based on 23 mapping units, but the soils were emphasis on mapping vegetation resources rather than the soils.
The history of soil science in Iceland is relatively young. Geologic aspects of the soils received considerable attention early on with the study of devided into three major groups, the freely drained soils (silt loams), poorly drained soils (peat soils) and the soils of the deserts (stony alluvial, aeolian, lag gravel, etc). At the time of Johanesson´s studies, the unique properties of Andosols were only beginning to be realized, which limits the volcanic ash layers, but dating of soils by volcanic ash layers was pioneered by the Icelandic geologist
Sigurdur Thorarinsson (1961).
The first comprehensive map of of Icelandic soils was printed in 1959 at a scale of 1:750,000 present applicability of this work. It is noteworthy, however, that Johannesson wrote in his monograph: “ …is the fact that many silt loam soils have some characteristics like those of the volcanic ash soils in other countries, for instance those of Japan, and thus perhaps might be
(Nygard and Johanesson 1959). Other soil survey efforts were localized and this map together with
Johannesson´s monograph on Icelandic soils
(1960) remained the only complete survey of
Icelandic soils until this year. considered as close relatives to or even as members of the so-called Ando soil group..”
After the work of Johannesson, emphasis was mainly on agronomic aspects of Icelandic soils,
In response to request made by the European Soil
Bureau and other international agencies, the such as fertilization of hay fields and draining of wetland soils. Noteworthy is Helgason's comprehensive account of soils of South-west
Agricultural Research Institute is now completing a soil map in the scale of 1:500,000.
Iceland (1963; 1968). Two Ph.D. dissertations added considerable knowledge on the basic
characteristics of Icelandic soils in the eighties by
Ólafsson (1974) and Guðmundsson (1978). The
Agricultural Research Institute is still involved in
The pioneer work by Johannesson (1960) established a framework for the classification of
Icelandic soils that is still valid. The soil map that was included in his monograph is attributed to Ivar
Nygard who started this work in 1951, but after
Nygard’s death, Johannesson completed the map in co-operation with the US Soil Conservation
Service. The map was printed by the U.S. Geologic
Survey in 1959, but was included with both the
Icelandic and English versions of Johannesson’s monograph on Icelandic soils (1960). The monograph was reprinted in Icelandic by the
Agricultural Research Institute in 1988. soil evaluation for fertilizer recommendations, and has carried out extensive research related to soil fertility. The results have been reported both in specialized reports and as scientific papers (e.g.,
Palmason et al.
, 1996; Palmason and Helgason,
1996).
Several attempts have been made to map soils in localized areas (e.g. Helgason and Gudbergsson,
1977; Gudbergsson and Olafsson, 1978), drawing much from the basis Johannesson provided.
Gudbergsson (1982) made an outline for the classification of wetland soils (Histosols).
Soil Survey and databases in Iceland. Ólafur Arnalds 91

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Soil mapping needs to be based on a suitable soil classification system. The Agricultural Research
Institute collaborated with Texas A&M University and the USDA-NRCS to provide a new perspective on Icelandic soils for this purpose, with detailed analyses of several representative soil pedons
(Arnalds, 1990; Arnalds et al.
, 1995; Arnalds and
Kimble, unpublished data; Wada et al.
, 1992).
These studies show that Icelandic soils are
Andosols and Andic integrates of other soil groups to a large extent. More recent overview of
Icelandic soils was published by Arnalds (1999a).
The soils of the barren areas in Iceland are quite different from the typical Andosols and Histosol that cover other parts of the country. Arnalds
(1988; 1990) and Gudmundsson (1991) have published studies on these soils. Arnalds and
Kimble conducted a detailed analysis of ten representative pedons of Icelandic desert soils but the results are still being analyzed.
A steady input of eolian materials and occasional tephra additions cause the organic carbon content to be lower than 25% in many of the wetland soils, resulting in Andisol (US-Soil Survey Staff, 1998) rather than Histosol classification (Arnalds et al.
,
1999). The desert soils are also often classified as
Andisol because of their high volcanic glass content.
The current edition of the US Soil Taxonomy (US
Soil Survey Staff, 1998) has therefore the disadvantage in relation to the classification of
Icelandic soils that it fails to distinguish between some of the major soil types at the highest level because of dominating andic influences.
This can also be judged as a benefit, demonstrating the dominating influence of andic soil properties of
Icelandic soils.
Applying the FAO soil classification (FAO, 1998) system involves similar problems as for the US system in that many contrasting soils are classified the same at the highest level as Andosols. The wetland soils often do not meet the cryterion for
Histosols because of relatively low organic content and the dominance of volcanic glass in desert soils often excludes Arenosols, Fluvisols, Cambisols and
Regosols as soil groups. However, Thorsteinn
Gudmundsson (1994) found that the FAO legend
(FAO-UNESCO, 1988) provided a good framwork for mapping soils in Iceland. He translated and adapted the FAO system for use in Iceland.
The Icelandic adoption of the FAO scheme for the soil groups (Gudmundsson, 1994) does not fully correlate with the FAO World Reference Base
(FAO 1998) for reasons stated above. Its use may therefore cause problems in relating Icelandic soil information at an international level although, with modifications, it is well suited for domestic use.
The Agricultural Research Institute is currently making an effort to produce a soil map in
1:500,000. Soil classification issues have not been resolved yet. A preliminary version of this map is published with this paper (Figure 1). The soil information underlying the map is drawn from published and unpublished literature on Icelandic soils, which currently is being compiled for a databank and an overview publication. Some general characteristics are presented in Table 1.
Soil analysis generally follows standard methods designed for Andosols such as described by
Blakemore et al.
, 1987. Soil descriptions generally follow US methods (eg., USDA-NRCS 1998).
Soil Class
Brown Andosols
Organic Andosols km 2
Depth m
OC
% pH in H
2
O
43 770 0.5-1.5 2-10 5.5-6.5
8 600 0.5-5 5-30 4.5-5.5
Oxalate
Al+1/2Fe%
3-8
>2
Clay
%
15-40
?
Vitric Andosols
Leptosols
‡
Sandy Andosols
†
1 8600
4 540
15 090
0.2-0.5
0-2
0.5-1.5
0.2-2
6.5-7.0
6.5-7.0
1-2
0.3-0.8
5-15
1-5
‡
No data available
†
Area (km 2 ) includes both Sandy Andosols and Sandy Andosols/Leptosol complex.
CEC
Meq/100g
10-40
30-60
5-15
2-10
H
2
5-15
O
15 bar
30-60
60-120
1-10
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Figure 1: Soil map of Iceland at 1:500,000 scale.
Soil Survey and databases in Iceland. Ólafur Arnalds 93

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The geographic information is mainly drawn from three sources:
1.
Vegetation maps . Vegetation reflects soil conditions, especially the distinction between wetlands (organic soils), freely drained vegetated Andosols and the deserts.
2.
Soil Erosion digital databases (see later in the paper). This information gives a good geomorphological overview of the desert surfaces, and is the primary source for their geographic information.
3.
Infrared satellite images (LANDSAT TM).
They are used where there is a lack of vegetation information. The images also provide the base map, correlated with
Iceland´s current map projection system.
The map was constructed using Arc/Info GIS software. The soil classes used in the map are as follows (note the class names are only suggestive at this stage and are subject to further development):
1.
Brown Andosols . These represent the typical
Andosols of Iceland. They are usually freely drained and have developed in eolian and tephra materials that typically form a 80-200 cm mantle that has accumulated over an older surface (usually glacial till or lava). They are rich in allophane clay minerals, and ferrihydrate, but volcanic glass is also in abundance near the most active volanoes.
Distinctive volcanic ash layers are common.
2.
Organic Andosols . These soils are found at poorly drained sites (bogs and myres), and often grade into Histosols. They most likely classify as Histosols in areas furthest away from eolian sources. The Organic Andosols are typically 50-500 cm thick with 5-30% C content. Volcanic ash layers are common.
3.
Vitric Andosols (or Gravelly Andosols) .
These soils are desert soils poor in organic matter compared to the classes above. They meet the criterion for Andosols (and Andisols) because of abundance of volcanic glass materials and other andic characteristics. The
Vitric Andosols grade into Regosols (away from eolian tephra sources) and Leptosols.
4.
Leptosols. These soils are found on scree slopes, recent lava surfaces, and on lava surfaces where erosion processes have removed Brown or Organic Andosols from the top.
5.
Sandy Andosols. Sandy surfaces are common in Iceland near glacial margins and on glaciofluvial floodplains. Eolian processes have often carried sandy materials long distances from their sources, increasing the size of sandy areas. The sand is largely composed of volcanic glass.
6.
Leptosol/Sandy Andosol complex. This is a special class as this combination is very common in Iceland. It occurs where there is an abundance of sand on lava surfaces (due to eolian processes and volcanic ash fall). The sand covers the depressions while bedrock
(lava surface) sticks out where the surface rises.
Two other soil classes can readily be applied into this system, but can not be included on a map at such a coarse scale. These are Gleysols and Fluvic
Andosols (which grade into Fluvisols, Gleysols and
Regosols).
Andosols in Iceland cover all together about
80,000 km 2 and therefore make up a substantial proportion of the Andosols in the world. The areal extent of Brown Andosols represents an overestimate for two reasons. One is that desert areas /patches are common within areas dominated by the Brown Andosols. The second is that the land classification system used includes some areas within this class where the soils are too shallow to meet the criteria for Andisol/Andosol. At this point, it is not possible to account for this error.
The three desert soil classes dominate about
38,000 km 2 , (actual extent is somewhat larger for the reason given above). They have vast potential for carbon sequestration associated with ecosystem restoration (Arnalds et al.
1999). No data is available for the Leptosols yet.
Soil erosion and degradation has been a major problem in Iceland since the arrival of man about
1100 years ago. The extent and severity of soil erosion in Iceland has been mapped at a scale of
1:100,000, by the Agricultural Research Institute and the Icelandic Soil Conservation Service.
Erosion processes in Iceland are extremely varied and conventional methods designed for estimating erosion in cultivated areas are of little use.
The erosion assessment is based on classification of erosion forms that can be identified in the landscape (Arnalds et al.
, 1997). The ARI-SCS erosion database is made of about 18,000 polygons. Each polygon is characterized by one or more erosion forms. Erosion severity for each of the erosion forms was estimated on a scale from zero to five, five being considered extremely severe erosion (Table 2).
94 Soil Survey and databases in Iceland. Ólafur Arnalds

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Erosion severity/map units
0 No erosion
1 Slight erosion
2 Moderate erosion
3 Considerable erosion
4 Severe erosion
5 Very severe erosion
Km 2
4 148
7 466
26 698
23 106
11 332
6 375
% Iceland
4
7
26
23
11
6
High mountains
Glaciers
Waters
9 794
11 361
1 436
10
11
1.4
Other 1 010 1
TOTAL 102 721
$: High mountains, glaciers, waters and ‘other’ excluded.
The overall results indicate the severity of erosion in Iceland, the scale of which is comparable only to very degraded, arid areas of the world. The combined total of considerable to very severe erosion is >50% of the country when high mountains and glaciers have been excluded. Much of this severe erosion occurs within the deserts, but severe erosion is also degrading large tracts of the remaining vegetated areas (see Arnalds et al.,
1997; Arnalds, 1999b).
Soil erosion continues to be monitored and mapped by the Icelandic SCS, in areas where it is most severe, but now at a larger scale (1:5,000 to
1:25,000).
% $
5.2
9.4
33.7
29.2
14.3
8.1
100 detail in a special issue of the Journal of
Agricultural Research in Iceland (Thorsteinsson,
1982). Much of this data has been digitized and the
Institute of Natural History has recently published a new vegetation map for all of Iceland in the scale of 1:500,000.
Although detailed soil maps have not been made for Iceland, much effort has been made to make vegetation maps. It was concluded around 1960 that vegetation maps would give more information about Icelandic nature than would soil maps, bearing in mind the major use of the land for grazing. It was expected that each of the vegetation mapping elements reveal information on the underlying soils.
Mapping of the vegetation was conducted by the
Agricultural Research Institute but the programme has recently been relocated at the Institute of
Natural History. Vegetation mapping has been completed for about 2/3 of the country at a scale of
1:40,000 in the highlands and 1:25,000 in lowland areas. Icelandic vegetation was split up into five major categories where drainage is the most influential factor.
These categories are divided into 14 associations and about 100 mapping elements. Deserts are mapped separately. The methods were described in
A central database for Icelandic soils is being established. The main use for soil data is related to soil fertility for hay production. Detailed soil research has also provided fundamental understanding to explain why the soils are extremely vulnerable to erosion. The national erosion database is used for various purposes such as land use planning, reclamation strategies, and policy-making.
Soil science is still a young science in Iceland. Few
Icelandic scientists have higher degrees in soil science. This is reflected in all too sparse research efforts. The Agricultural Research Institute has plans to increase its current research on the formation and basic properties of Icelandic soils.
Currently, there is no systematic monitoring of soil fertility and quality, but plans have been made for such activities. Mapping of soil resources will become more important with increased emphasis on GIS databases for land capability assessment and land use planning in Iceland. Improved basic understanding of soil behaviour will also become important in the near future for maintaining soil quality and for monitoring pollution.
Arnalds, O. (1988). Soils of denuded areas in
Iceland. Natturufraedingurinn 58:101-116. In
Icelandic, English summary.
Soil Survey and databases in Iceland. Ólafur Arnalds 95

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Arnalds, O. (1990). Characterization and erosion of Andosols in Iceland. Ph.D. Dissertation,
Texas A&M University, College Station,
Texas, U.S.A.
Arnalds, O. (1999a). Soils and Soil Erosion in
Iceland. In: H. Armannson (ed), The fifth
International Symposium on the Geochemistry of the Earth’s Crust. Calcema, Rotterdam, The
Netherlands. In Press.
Arnalds, O. (1999b). The Icelandic ´rofabard´ erosion features. Earth Surface Processes and
Landforms. In press.
Arnalds, O., C.T. Hallmark, and L.P. Wilding.
(1995). Andisols from four different regions of
Iceland. Soil Science Society of America
Journal, 59:161-169.
Arnalds, O., A.L. Aradottir and G. Gudbergsson.
(1999). Organic carbon sequestration by restoration of degraded areas in Iceland. In: R.
Lal, J. Kimble and R. Folleett (eds.)
Assessment for soil organic carbon pools.
Advances in Soil Science. In print.
Arnalds, O., E.F. Thorarinsdottir, S.
Metusalemsson, A. Jonsson, E. Gretarsson, and
A. Arnason. (1997). Soil Erosion in Iceland.
Icelandic SCS and the Agricultural Research
Institute, Reykjavik, Iceland. In Icelandic.
Baldwin, M., C.E. Kellogg, and J. Thorp. (1938).
Soil Classification. U.S. Dept. Agriculture
Yearbook (Soils and Men) 1938:979-1001.
FAO-UNESCO. (1988). Soil map of the world,
Revised Legend. FAO, Rome, Italy.
FAO. (1998). World reference base for soil resources. FAO, ISRIC, ISSS, Rome, Italy.
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Gudbergsson, G. (1982). Classification of wetland soils. In: A. Snaebjornsson. Wetland soils.
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Report 16. In Icelandic.
Gudmundsson, Th. (1978). Pedological studies of
Icelandic peat soils. Ph.D. Thesis, University of
Aberdeen, Scotland.
Gudmundsson, Th. (1991). Soil research on reclamation sites in central Iceland. In: I.
Thorsteinsson (ed). Reclamation on the
Audkuluheidi and Eyvindarstadaheidi commons. p. 51-70. In Icelandic.
Gudmundsson, Th. (1994). The FAO soil classification system, with Icelandic adaptions.
RALA Report No 167.
Helgason, B. (1963). Basaltic soils of South-west
Iceland. I. Journal of Soil Science 14:64-72.
Helgason, B. (1968). Basaltic soils of South-west
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Helgason, B. and G. Gudbergsson. (1977).
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Johannesson, B. (1960). The Soils of Iceland.
University Research Institute, Reykjavik,
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Palmason, F. and B. Helgason (1996). Comparison of methods estimating available phosphorus and potassium in grassland soil. Icelandic
Agricultural Sciences 3:3-11.
Palmason, F.H. Thorgeirsson, H. Sigurdardottir, H.
Bjornsson, and O. Arnalds. 1996. Nitrogen mineralization in soil. Icelandic Agricultural
Science 10: 185-208. In Icelandic, English summary.
Thorarinsson, S. (1961). Wind erosion in Iceland.
A tephrocronological study. Icelandic Forestry
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96 Soil Survey and databases in Iceland. Ólafur Arnalds